Differences in the timing of migration between ages and sexes within
songbird species have been well documented. In general, males migrate 2 - 10 days before females during
spring. Further, adult birds generally migrate before young (second year) birds in spring. Patterns in the autumn are far less clear.
We tested for differential migration patterns by examining data from 26,002 individuals of 115 species captured at Braddock Bay and Hamlin Beach between April 22 - June 8 and September 3 - October 17 in 1999 and 2000. Significant differences between sex and age classes in the timing of passage were detected during both spring and autumn.
Sex-based differences in the timing of migration were most pronounced in spring, when the mean passage date for males significantly preceded the mean date for females in 17 of 19 species
1). The difference in mean passage dates ranged from 1.8 days to 10.4 days, with a mean of 5.8 days. Sex-based differential migration during autumn was less pronounced than during spring, with only 6 of 11 species demonstrating significant differences
(Table 1). Males preceded females in two species, while females preceded males in four species. The absolute difference in mean passage dates was less than 4 days in all cases, and averaged 2.5 days.
Age-based differences in the timing of migration were pronounced in spring, with adult (after second year) birds preceding yearling (second year) birds in 17 of 21 species analyzed
(Table 2). On average, adults preceded yearlings by 5.1 days. Age-based differential migration patterns during autumn were less clear, as significant differences were only detected in seven of 20 species. Of these, young (hatch year) birds passed through earlier than adult (after hatch year) birds in six species, with the reverse pattern detected in one species
(Table 3). The absolute difference in mean passage dates averaged 3.7 days.
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